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<a href="protocol__negotiator_8hpp.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno">    1</span><span class="comment">/* Flow-IPC: Core</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno">    2</span><span class="comment"> * Copyright 2023 Akamai Technologies, Inc.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno">    3</span><span class="comment"> *</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno">    4</span><span class="comment"> * Licensed under the Apache License, Version 2.0 (the</span></div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno">    5</span><span class="comment"> * &quot;License&quot;); you may not use this file except in</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno">    6</span><span class="comment"> * compliance with the License.  You may obtain a copy</span></div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno">    7</span><span class="comment"> * of the License at</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno">    8</span><span class="comment"> *</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno">    9</span><span class="comment"> *   https://www.apache.org/licenses/LICENSE-2.0</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno">   10</span><span class="comment"> *</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno">   11</span><span class="comment"> * Unless required by applicable law or agreed to in</span></div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno">   12</span><span class="comment"> * writing, software distributed under the License is</span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno">   13</span><span class="comment"> * distributed on an &quot;AS IS&quot; BASIS, WITHOUT WARRANTIES OR</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno">   14</span><span class="comment"> * CONDITIONS OF ANY KIND, either express or implied.</span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno">   15</span><span class="comment"> * See the License for the specific language governing</span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno">   16</span><span class="comment"> * permissions and limitations under the License. */</span></div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno">   17</span><span class="comment"></span> </div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno">   18</span><span class="comment">/// @file</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno">   19</span><span class="comment"></span><span class="preprocessor">#pragma once</span></div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno">   20</span> </div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno">   21</span><span class="preprocessor">#include &quot;<a class="code" href="common_8hpp.html">ipc/common.hpp</a>&quot;</span></div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno">   22</span><span class="preprocessor">#include &quot;<a class="code" href="util__fwd_8hpp.html">ipc/util/util_fwd.hpp</a>&quot;</span></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno">   23</span><span class="preprocessor">#include &lt;flow/log/log.hpp&gt;</span></div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno">   24</span> </div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno">   25</span><span class="keyword">namespace </span><a class="code hl_namespace" href="namespaceipc_1_1transport.html">ipc::transport</a></div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno">   26</span>{</div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno">   27</span><span class="comment"></span> </div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno">   28</span><span class="comment">/**</span></div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno">   29</span><span class="comment"> * A simple state machine that, assuming the opposide side of a comm pathway uses an equivalent state machine,</span></div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno">   30</span><span class="comment"> * helps negotiate the protocol version to speak over that pathway, given each side being capable of speaking</span></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno">   31</span><span class="comment"> * a range of protocol versions and reporting the highest such version to the other side.  By *comm pathway*</span></div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno">   32</span><span class="comment"> * we mean a bidirectional communication channel of some sort with two mutually-opposing endpoints (it need</span></div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno">   33</span><span class="comment"> * not be full-duplex).</span></div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno">   34</span><span class="comment"> *</span></div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno">   35</span><span class="comment"> * It is copyable and movable, so that the containing object can be copyable and movable too.</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno">   36</span><span class="comment"> * A moved-from `*this` becomes as-if it was just constructed.</span></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno">   37</span><span class="comment"> *</span></div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno">   38</span><span class="comment"> * The algorithm followed is quite straightforward and is exposed completely in the contract of this simple API:</span></div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno">   39</span><span class="comment"> * The impetus behind this class is not for it to be able to perform some complex `private` operations but rather</span></div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno">   40</span><span class="comment"> * to provide a reusable component that both internal and (optionally) user code can reliably count on to apply</span></div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno">   41</span><span class="comment"> * the same consistent rules.  So while it does some minimal work, its main value is in presenting a common</span></div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno">   42</span><span class="comment"> * algorithm that (1) achieves protocol negotiation and (2) doesn&#39;t shoot ourselves in the foot in the face</span></div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno">   43</span><span class="comment"> * of future protocol changes.</span></div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno">   44</span><span class="comment"> *</span></div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno">   45</span><span class="comment"> * ### The algorithm ###</span></div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno">   46</span><span class="comment"> * A Protocol_negotiator `*this` assumes it is used by a single open comm pathway&#39;s local endpoint, and that a</span></div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno">   47</span><span class="comment"> * logically-equivalent Protocol_negotiator (or equivalent sofwatre) is used in symmetrical fashion by the opposide</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno">   48</span><span class="comment"> * side&#39;s endpoint.  (For example, a Native_socket_stream in PEER state uses a Protocol_negotiator internally,</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno">   49</span><span class="comment"> * and it therefore assumes the opposing Native_socket_stream does the same.)</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno">   50</span><span class="comment"> *</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno">   51</span><span class="comment"> * Further we assume that there is a range of protocols for the comm pathway, such that at least version 1</span></div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno">   52</span><span class="comment"> * (the initial version) exists, and versions 2, 3, ... may be developed (or have already been developed).</span></div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno">   53</span><span class="comment"> * There is understood to be no ambiguity as to what a version X of the protocol means: so, if certain software</span></div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno">   54</span><span class="comment"> * knows about version X at all, then what it understands protocol version X to be is exactly equal to what any</span></div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno">   55</span><span class="comment"> * other software (that also knows of version X) understands about protocol version X.</span></div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno">   56</span><span class="comment"> *   - We (the local endpoint) can speak a range of versions of the protocol: [L, H] with H &gt;= L &gt;= 1.</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno">   57</span><span class="comment"> *     Obviously we know L and H: i.e., the code instantiating `*this` knows L and H (in fact it gives them</span></div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno">   58</span><span class="comment"> *     to our ctor).</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno">   59</span><span class="comment"> *     - Note: Informally, one can think of H being the *preferred* version for us: We want to speak it if possible.</span></div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno">   60</span><span class="comment"> *       However, if necessary, we can invoke alternative code paths to speak a lower version for compatibility.</span></div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno">   61</span><span class="comment"> *   - They (the opposing endpoint) can similarly speak a range [Lp, Hp], with Hp &gt; Lp &gt;= 1.</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno">   62</span><span class="comment"> *     However we do not, at first at least, know Lp nor Hp.</span></div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno">   63</span><span class="comment"> *   - Each side shall speak the *highest* possible version of the protocol such that:</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno">   64</span><span class="comment"> *     - It is in range [L, H].</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno">   65</span><span class="comment"> *     - It is in range [Lp, Hp].</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno">   66</span><span class="comment"> *   - Therefore there are two possibilities:</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno">   67</span><span class="comment"> *     - If there is *no* such version, then the comm pathway cannot proceed: they have no protocol version in common</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno">   68</span><span class="comment"> *       they can both speak.  The pathway should close ASAP upon either side realizing this.</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno">   69</span><span class="comment"> *     - If there is such a version, then the comm pathway can proceed.  All we need is for *each side* to determine</span></div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno">   70</span><span class="comment"> *       what that version V is.  Naturally each side must come to the same answer.</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno">   71</span><span class="comment"> *</span></div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno">   72</span><span class="comment"> * While there are various ways to achieve this, including a back-and-forth negotiation, we opt for something quite</span></div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno">   73</span><span class="comment"> * simple and symmetrical.  (Recall that the opposide side is assumed to have a Protocol_negotiator (equivalent)</span></div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno">   74</span><span class="comment"> * following the same logic, and neither side shall be chosen (in our context) to be different from the other.</span></div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno">   75</span><span class="comment"> * E.g., there&#39;s no client and server dichotomy -- even if in the subsequently negotiated protocol there is; that&#39;s</span></div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno">   76</span><span class="comment"> * none of our business.)  The procedure:</span></div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno">   77</span><span class="comment"> *   - We send H to them, ASAP.</span></div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno">   78</span><span class="comment"> *     - Similarly they send Hp to us.</span></div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno">   79</span><span class="comment"> *   - Having received their Hp, we choose V = min(H, Hp).</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno">   80</span><span class="comment"> *     - Similarly having received our H, they choose V = min(H, Hp).  Important: This value V *is* the same on each</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno">   81</span><span class="comment"> *       side.  However the next computation will potentially differ between the 2 sides.</span></div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno">   82</span><span class="comment"> *   - On our side: If V &lt; L (which is possible only if V = Hp, meaning Hp &gt; H, meaning we are more advanced than</span></div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno">   83</span><span class="comment"> *     they are), we are insufficiently backwards-compatible.  Therefore V = UNSUPPORTED.  We should</span></div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno">   84</span><span class="comment"> *     close the comm pathway ASAP.</span></div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno">   85</span><span class="comment"> *     - Similarly, on their side, if V &lt; Lp -- they are more advanced than we are, and they don&#39;t speak enough</span></div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno">   86</span><span class="comment"> *       older versions to accomodate us -- then they will detect that V = UNSUPPORTED and should close the comm</span></div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno">   87</span><span class="comment"> *       pathway ASAP.</span></div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno">   88</span><span class="comment"> *   - On our side: Otherwise (V &gt;= L), speak V from this point on.</span></div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno">   89</span><span class="comment"> *     - Similarly, on ther side, if V &gt;= Lp, they shall speak V from this point on.</span></div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno">   90</span><span class="comment"> *</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno">   91</span><span class="comment"> * The role of Protocol_negotiator is simple:</span></div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno">   92</span><span class="comment"> *   - It memorizes the local L and H as passed to its ctor, and it starts with V = UNKNOWN.  negotiated_proto_ver()</span></div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno">   93</span><span class="comment"> *     always simply returns V which is the chief output of a `*this`.</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno">   94</span><span class="comment"> *   - Upon receiving Hp, user gives it to compute_negotiated_proto_ver(); this computes V based on the above</span></div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno">   95</span><span class="comment"> *     algorithm; namely: `(H &lt;= Hp) ? H : ((Hp &gt;= L) ? Hp : UNSUPPORTED)`.  So negotiated_proto_ver() shall return</span></div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno">   96</span><span class="comment"> *     that value (one of H, Hp, #S_VER_UNSUPPORTED) from then on.</span></div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno">   97</span><span class="comment"> *     - compute_negotiated_proto_ver() shall not be called again.  One can check</span></div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno">   98</span><span class="comment"> *     `negotiated_proto_ver() == S_VER_UNKNOWN`, if one would rather not independently keep track of whether</span></div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno">   99</span><span class="comment"> *     compute_negotiated_proto_ver() has been called yet or not.</span></div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno">  100</span><span class="comment"> *   - local_max_proto_ver_for_sending() shall return H once; after that UNSUPPORTED.  This is to encourage/help</span></div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno">  101</span><span class="comment"> *     the sending-out of our H exactly once, no more.</span></div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno">  102</span><span class="comment"> *</span></div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno">  103</span><span class="comment"> * Couple notes:</span></div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno">  104</span><span class="comment"> *   - If H = Hp, then everyone will agree on everything and just speak H.  This is perhaps most typical.</span></div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno">  105</span><span class="comment"> *     Usually then L = Lp also, but it&#39;s conceivable they&#39;re not equal (e.g. one side has a backwards-compatibility</span></div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno">  106</span><span class="comment"> *     patch but not the other).  It doesn&#39;t matter really.</span></div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno">  107</span><span class="comment"> *   - Otherwise, though, there are 2 possibilities:</span></div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno">  108</span><span class="comment"> *     - Both sides agree on the same V, with no V = UNSUPPORTED.  This occurs, if in fact there is overlap between</span></div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno">  109</span><span class="comment"> *       [L, H] and [Lp, Hp], just Hp &gt; H or vice versa: One gets to speak its &quot;preferred&quot; protocol, while the other</span></div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno">  110</span><span class="comment"> *       has to speak an earlier version.</span></div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno">  111</span><span class="comment"> *     - One side detects V = UNSUPPORTED (the other does not).  This occurs, if one side is so much newer than the</span></div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno">  112</span><span class="comment"> *       other, it doesn&#39;t even have backwards-compatibility support for the other side.  (And/or perhaps the</span></div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno">  113</span><span class="comment"> *       protocol does not attempt to ever be backwards-compatible; so H = L and Hp = Lp always.)</span></div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno">  114</span><span class="comment"> *       - In this case one side will try to proceed; but it won&#39;t get far, as the other (more advanced) side</span></div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno">  115</span><span class="comment"> *         will close the comm pathway instead of either sending or receiving anything beyond its H or Hp.</span></div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno">  116</span><span class="comment"> *</span></div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno">  117</span><span class="comment"> * We could have avoided the latter asymmetric situation by sending over both L and H (and they both Lp and</span></div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno">  118</span><span class="comment"> * Hp); then both sides would do exactly the same computation.  However it seems an unnecessary complication</span></div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno">  119</span><span class="comment"> * and payload.</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno">  120</span><span class="comment"> *</span></div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno">  121</span><span class="comment"> * ### Key tip: Coding for version-1 versus one version versus multiple versions ###</span></div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno">  122</span><span class="comment"> * Using a `*this` is in and ofi itself extremely simple; just look at the API and/or read the above.  What is somewhat</span></div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno">  123</span><span class="comment"> * more subtle is how to organize your comm pathway&#39;s behavior around the start, when the negotiation occurs.</span></div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno">  124</span><span class="comment"> * That part is also straightforward for the most part:</span></div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno">  125</span><span class="comment"> *   - Before you send out your first stuff, or possibly together with it, send an encoding of</span></div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno">  126</span><span class="comment"> *     local_max_proto_ver_for_sending().</span></div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno">  127</span><span class="comment"> *   - When reading your first stuff, read the similar encoding from the opposing side.</span></div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno">  128</span><span class="comment"> *     Now compute_negotiated_proto_ver() will determine negotiated_proto_ver(); call it V.  From this point on:</span></div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno">  129</span><span class="comment"> *     - Anything you receive should be interpreted per protocol version V.</span></div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno">  130</span><span class="comment"> *       - This is straightforward: since the stuff that makes it possible to determine V comes first, anytime</span></div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno">  131</span><span class="comment"> *         you need to know how to interpret anything else, you&#39;ll know V already.</span></div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno">  132</span><span class="comment"> *     - Anything you send should be according to protocol version V.</span></div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno">  133</span><span class="comment"> *</span></div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno">  134</span><span class="comment"> * That last part is the only subtle part.  The potential challenge is that if you want to send something, you may</span></div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno">  135</span><span class="comment"> * not have gotten the protocol-negotiation in-message yet; in which case you do *not* know V.  If it is necessary</span></div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno">  136</span><span class="comment"> * to know it at that point, then there&#39;s no choice but to enter a would-block state of sorts, during which time</span></div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno">  137</span><span class="comment"> * any out-messages would need to be internally queued or otherwise deferred, until you do know V (have received</span></div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno">  138</span><span class="comment"> * the first in-message and called compute_negotiated_proto_ver()).  Protocol_negotiator offers no help as such.</span></div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno">  139</span><span class="comment"> *</span></div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno">  140</span><span class="comment"> * However there are several common situations where this concern is entirely mitigated away.  If it applies to you,</span></div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno">  141</span><span class="comment"> * then you will have no problem.</span></div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno">  142</span><span class="comment"> *   - If `local_min_proto_ver == local_max_proto_ver` (to ctor, a/k/a L = H in the above algorithm sketch),</span></div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno">  143</span><span class="comment"> *     meaning locally you support only one protocol version, then there is no ambiguity in any case.</span></div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno">  144</span><span class="comment"> *     You know which protocol you&#39;ll speak.  The only ways there&#39;d be a problem are: (1) compute_negotiated_proto_ver()</span></div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno">  145</span><span class="comment"> *     determines incompatibility -- by which point the supposed problem is moot; and (2) the other side</span></div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno">  146</span><span class="comment"> *     does the same -- in which case it will close the comm pathway (not our problem, by design).</span></div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno">  147</span><span class="comment"> *     - In particular, if L = H = 1 -- in the first release of the protocol -- this is of course the case.</span></div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno">  148</span><span class="comment"> *     - If you do not maintain backwards compatibility (e.g., L = H = 2, then next time L = H = 3, then... etc.),</span></div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno">  149</span><span class="comment"> *       then this is also the case.</span></div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno">  150</span><span class="comment"> *   - If L does not equal H, in many (most?) cases the actual negotiated version V does not affect many (most)</span></div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno">  151</span><span class="comment"> *     messages sent.  E.g., if you have a &quot;ping&quot; message, perhaps it will never change in any version of the</span></div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno">  152</span><span class="comment"> *     protocol.</span></div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno">  153</span><span class="comment"> *     - So the problem only occurs when there&#39;s actual ambiguity about what to send.  Your code may still need to be</span></div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno">  154</span><span class="comment"> *       somewhat more complex than the L=H case, but perf/responsiveness at least is less likely to be affected.</span></div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno">  155</span><span class="comment"> *   - If your protocol has a built-in handshake/log-in/etc. phase (where one set side is expected to send</span></div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno">  156</span><span class="comment"> *     a SYN-like thing, and the other side is supposed to reply with an ACK of some kind in response), then you</span></div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno">  157</span><span class="comment"> *     can specifically:</span></div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno">  158</span><span class="comment"> *     - Not add any version-dependent payload to the SYN-like (opening) message; or at least defer any such</span></div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno">  159</span><span class="comment"> *       version-dependent interpretation thereof, until V is known shortly.</span></div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno">  160</span><span class="comment"> *     - But, do include the version in the SYN-like (opening) message and to its ACK-like response, specifically.</span></div>
<div class="line"><a id="l00161" name="l00161"></a><span class="lineno">  161</span><span class="comment"> *       By the time the hand-shake completes, both sides know V and can proceed.</span></div>
<div class="line"><a id="l00162" name="l00162"></a><span class="lineno">  162</span><span class="comment"> *</span></div>
<div class="line"><a id="l00163" name="l00163"></a><span class="lineno">  163</span><span class="comment"> * @note In general, for the case of initial-protocol-release -- version 1 -- the usefulness of Protocol_negotiator</span></div>
<div class="line"><a id="l00164" name="l00164"></a><span class="lineno">  164</span><span class="comment"> *       minimal, but it does exist.  It is minimal, because *assuming* both sides promise to follow this</span></div>
<div class="line"><a id="l00165" name="l00165"></a><span class="lineno">  165</span><span class="comment"> *       algorithm, then *all* the code actually *needs* to do is: (1) send `H = 1` in some fashion that will never</span></div>
<div class="line"><a id="l00166" name="l00166"></a><span class="lineno">  166</span><span class="comment"> *       change in the future; (2) receive Hp in some fashion that will never change in the future either; and</span></div>
<div class="line"><a id="l00167" name="l00167"></a><span class="lineno">  167</span><span class="comment"> *       (3) explode, if Hp is not present or is not 1.  This is very much doable without Protocol_negotiator.</span></div>
<div class="line"><a id="l00168" name="l00168"></a><span class="lineno">  168</span><span class="comment"> *       However it is almost equally easy with Protocol_negotiator, too; and it *is a good practice* to leverage it,</span></div>
<div class="line"><a id="l00169" name="l00169"></a><span class="lineno">  169</span><span class="comment"> *       so that if there is a version 2 later, the conventions in force will be unambiguous.  Only then it *might*</span></div>
<div class="line"><a id="l00170" name="l00170"></a><span class="lineno">  170</span><span class="comment"> *       be necessary to worry about the subtle situation above, where we want to send something out whose expression</span></div>
<div class="line"><a id="l00171" name="l00171"></a><span class="lineno">  171</span><span class="comment"> *       depends on V, but we haven&#39;t received the protocol-negotiating in-message yet and hence don&#39;t know V yet.</span></div>
<div class="line"><a id="l00172" name="l00172"></a><span class="lineno">  172</span><span class="comment"> *</span></div>
<div class="line"><a id="l00173" name="l00173"></a><span class="lineno">  173</span><span class="comment"> * ### Safety, trust assumption ###</span></div>
<div class="line"><a id="l00174" name="l00174"></a><span class="lineno">  174</span><span class="comment"> * We emphasize that this is not authentication.  There is the implicit trust that the opposing side will be using</span></div>
<div class="line"><a id="l00175" name="l00175"></a><span class="lineno">  175</span><span class="comment"> * a very specific *protocol for determining the rest of the protocol* and trust us to do the same.  Furthermore</span></div>
<div class="line"><a id="l00176" name="l00176"></a><span class="lineno">  176</span><span class="comment"> * there&#39;s implicit trust that the protocol versions being referred-to mean the same thing on both sides.</span></div>
<div class="line"><a id="l00177" name="l00177"></a><span class="lineno">  177</span><span class="comment"> *</span></div>
<div class="line"><a id="l00178" name="l00178"></a><span class="lineno">  178</span><span class="comment"> * To establish this trust is well beyond the mission of `*this` class; and explaining how to do so is well beyond</span></div>
<div class="line"><a id="l00179" name="l00179"></a><span class="lineno">  179</span><span class="comment"> * this doc header.</span></div>
<div class="line"><a id="l00180" name="l00180"></a><span class="lineno">  180</span><span class="comment"> *</span></div>
<div class="line"><a id="l00181" name="l00181"></a><span class="lineno">  181</span><span class="comment"> * ### Thread safety ###</span></div>
<div class="line"><a id="l00182" name="l00182"></a><span class="lineno">  182</span><span class="comment"> * For the same `*this`, the standard default assumptions apply (mutating access disallowed concurrently with</span></div>
<div class="line"><a id="l00183" name="l00183"></a><span class="lineno">  183</span><span class="comment"> * any other access) with the following potentially important exception: local_max_proto_ver_for_sending() can</span></div>
<div class="line"><a id="l00184" name="l00184"></a><span class="lineno">  184</span><span class="comment"> * be executed concurrently with any other API except itself.  In other words, the outgoing-direction</span></div>
<div class="line"><a id="l00185" name="l00185"></a><span class="lineno">  185</span><span class="comment"> * (local_max_proto_ver_for_sending()) and incoming-direction work</span></div>
<div class="line"><a id="l00186" name="l00186"></a><span class="lineno">  186</span><span class="comment"> * (compute_negotiated_proto_ver(), negotiated_proto_ver()) can be safely performed independently/concurrently</span></div>
<div class="line"><a id="l00187" name="l00187"></a><span class="lineno">  187</span><span class="comment"> * w/r/t each other.</span></div>
<div class="line"><a id="l00188" name="l00188"></a><span class="lineno">  188</span><span class="comment"> */</span></div>
<div class="line"><a id="l00189" name="l00189"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html">  189</a></span><span class="keyword">class </span><a class="code hl_class" href="classipc_1_1transport_1_1Protocol__negotiator.html">Protocol_negotiator</a> :</div>
<div class="line"><a id="l00190" name="l00190"></a><span class="lineno">  190</span>  <span class="keyword">public</span> flow::log::Log_context</div>
<div class="line"><a id="l00191" name="l00191"></a><span class="lineno">  191</span>{</div>
<div class="line"><a id="l00192" name="l00192"></a><span class="lineno">  192</span><span class="keyword">public</span>:</div>
<div class="line"><a id="l00193" name="l00193"></a><span class="lineno">  193</span>  <span class="comment">// Types.</span></div>
<div class="line"><a id="l00194" name="l00194"></a><span class="lineno">  194</span><span class="comment"></span> </div>
<div class="line"><a id="l00195" name="l00195"></a><span class="lineno">  195</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00196" name="l00196"></a><span class="lineno">  196</span><span class="comment">   * Type sufficient to store a protocol version; positive values identify newer versions of a protocol;</span></div>
<div class="line"><a id="l00197" name="l00197"></a><span class="lineno">  197</span><span class="comment">   * while non-positive values S_VER_UNKNOWN and S_VER_UNSUPPORTED are special values.</span></div>
<div class="line"><a id="l00198" name="l00198"></a><span class="lineno">  198</span><span class="comment">   */</span></div>
<div class="line"><a id="l00199" name="l00199"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">  199</a></span>  <span class="keyword">using </span><a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> = int16_t;</div>
<div class="line"><a id="l00200" name="l00200"></a><span class="lineno">  200</span> </div>
<div class="line"><a id="l00201" name="l00201"></a><span class="lineno">  201</span>  <span class="comment">// Constants.</span></div>
<div class="line"><a id="l00202" name="l00202"></a><span class="lineno">  202</span><span class="comment"></span> </div>
<div class="line"><a id="l00203" name="l00203"></a><span class="lineno">  203</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00204" name="l00204"></a><span class="lineno">  204</span><span class="comment">   * A #proto_ver_t value, namely zero, which is a reserved value indicating &quot;unsupported version&quot;; it is not</span></div>
<div class="line"><a id="l00205" name="l00205"></a><span class="lineno">  205</span><span class="comment">   * a valid version number identifying a protocol that can actually be spoken by relevant software.  Its specific</span></div>
<div class="line"><a id="l00206" name="l00206"></a><span class="lineno">  206</span><span class="comment">   * meaning is identified specifically where it might be returned or taken by the API.</span></div>
<div class="line"><a id="l00207" name="l00207"></a><span class="lineno">  207</span><span class="comment">   */</span></div>
<div class="line"><a id="l00208" name="l00208"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#a126eb85013fbeb11bcee34efbf0c79da">  208</a></span>  <span class="keyword">static</span> <span class="keyword">constexpr</span> <a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> <a class="code hl_variable" href="classipc_1_1transport_1_1Protocol__negotiator.html#a126eb85013fbeb11bcee34efbf0c79da">S_VER_UNSUPPORTED</a> = 0;</div>
<div class="line"><a id="l00209" name="l00209"></a><span class="lineno">  209</span><span class="comment"></span> </div>
<div class="line"><a id="l00210" name="l00210"></a><span class="lineno">  210</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00211" name="l00211"></a><span class="lineno">  211</span><span class="comment">   * A #proto_ver_t value, namely a negative one, which is a reserved value indicating &quot;unknown version&quot;; it is not</span></div>
<div class="line"><a id="l00212" name="l00212"></a><span class="lineno">  212</span><span class="comment">   * a valid version number identifying a protocol that can actually be spoken by relevant software.  Its specific</span></div>
<div class="line"><a id="l00213" name="l00213"></a><span class="lineno">  213</span><span class="comment">   * meaning is identified specifically where it might be returned or taken by the API.</span></div>
<div class="line"><a id="l00214" name="l00214"></a><span class="lineno">  214</span><span class="comment">   */</span></div>
<div class="line"><a id="l00215" name="l00215"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#aa7e47f4f6a700aeaa9600a5426a17292">  215</a></span>  <span class="keyword">static</span> <span class="keyword">constexpr</span> <a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> <a class="code hl_variable" href="classipc_1_1transport_1_1Protocol__negotiator.html#aa7e47f4f6a700aeaa9600a5426a17292">S_VER_UNKNOWN</a> = -1;</div>
<div class="line"><a id="l00216" name="l00216"></a><span class="lineno">  216</span> </div>
<div class="line"><a id="l00217" name="l00217"></a><span class="lineno">  217</span>  <span class="comment">// Constructors/destructor.</span></div>
<div class="line"><a id="l00218" name="l00218"></a><span class="lineno">  218</span><span class="comment"></span> </div>
<div class="line"><a id="l00219" name="l00219"></a><span class="lineno">  219</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00220" name="l00220"></a><span class="lineno">  220</span><span class="comment">   * Constructs a comm pathway&#39;s negotiator object in initial state wherein: (1) negotiated_proto_ver()</span></div>
<div class="line"><a id="l00221" name="l00221"></a><span class="lineno">  221</span><span class="comment">   * returns #S_VER_UNKNOWN (not yet negotiated with opposing Protocol_negotiator); and (2) we&#39;ve not yet</span></div>
<div class="line"><a id="l00222" name="l00222"></a><span class="lineno">  222</span><span class="comment">   * sent `local_max_proto_ver` to opposing side via first being queried using local_max_proto_ver_for_sending().</span></div>
<div class="line"><a id="l00223" name="l00223"></a><span class="lineno">  223</span><span class="comment">   *</span></div>
<div class="line"><a id="l00224" name="l00224"></a><span class="lineno">  224</span><span class="comment">   * @param logger_ptr</span></div>
<div class="line"><a id="l00225" name="l00225"></a><span class="lineno">  225</span><span class="comment">   *        Logger to use for logging subsequently.</span></div>
<div class="line"><a id="l00226" name="l00226"></a><span class="lineno">  226</span><span class="comment">   * @param nickname</span></div>
<div class="line"><a id="l00227" name="l00227"></a><span class="lineno">  227</span><span class="comment">   *        String to use subsequently in logging to identify `*this`.</span></div>
<div class="line"><a id="l00228" name="l00228"></a><span class="lineno">  228</span><span class="comment">   * @param local_max_proto_ver</span></div>
<div class="line"><a id="l00229" name="l00229"></a><span class="lineno">  229</span><span class="comment">   *        The highest version of the protocol the comm pathway can speak; a/k/a the preferred version.</span></div>
<div class="line"><a id="l00230" name="l00230"></a><span class="lineno">  230</span><span class="comment">   *        Positive or undefined behavior (assertion may trip).</span></div>
<div class="line"><a id="l00231" name="l00231"></a><span class="lineno">  231</span><span class="comment">   * @param local_min_proto_ver</span></div>
<div class="line"><a id="l00232" name="l00232"></a><span class="lineno">  232</span><span class="comment">   *        The lowest version of the protocol the comm pathway can speak; so either `local_max_proto_ver`</span></div>
<div class="line"><a id="l00233" name="l00233"></a><span class="lineno">  233</span><span class="comment">   *        (if our side has no backwards compatibility) or the oldest version with which we are backwards-compatible.</span></div>
<div class="line"><a id="l00234" name="l00234"></a><span class="lineno">  234</span><span class="comment">   *        Positive and at most `local_max_proto_ver` or undefined behavior (assertion may trip).</span></div>
<div class="line"><a id="l00235" name="l00235"></a><span class="lineno">  235</span><span class="comment">   */</span></div>
<div class="line"><a id="l00236" name="l00236"></a><span class="lineno">  236</span>  <span class="keyword">explicit</span> <a class="code hl_function" href="classipc_1_1transport_1_1Protocol__negotiator.html#a427c54f57df581027a330eb0f7146904">Protocol_negotiator</a>(flow::log::Logger* logger_ptr, <a class="code hl_typedef" href="namespaceipc_1_1util.html#ae6ac47812a90d1287c61e0b7de7bc4f5">util::String_view</a> nickname,</div>
<div class="line"><a id="l00237" name="l00237"></a><span class="lineno">  237</span>                               <a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> local_max_proto_ver, <a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> local_min_proto_ver);</div>
<div class="line"><a id="l00238" name="l00238"></a><span class="lineno">  238</span><span class="comment"></span> </div>
<div class="line"><a id="l00239" name="l00239"></a><span class="lineno">  239</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00240" name="l00240"></a><span class="lineno">  240</span><span class="comment">   * Copy-constructs `*this` to be equal to `src` object.</span></div>
<div class="line"><a id="l00241" name="l00241"></a><span class="lineno">  241</span><span class="comment">   *</span></div>
<div class="line"><a id="l00242" name="l00242"></a><span class="lineno">  242</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l00243" name="l00243"></a><span class="lineno">  243</span><span class="comment">   *        Source object.</span></div>
<div class="line"><a id="l00244" name="l00244"></a><span class="lineno">  244</span><span class="comment">   */</span></div>
<div class="line"><a id="l00245" name="l00245"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#ae4a1edcf2f1a0ae3e86b2ab93b71da0f">  245</a></span>  <a class="code hl_function" href="classipc_1_1transport_1_1Protocol__negotiator.html#ae4a1edcf2f1a0ae3e86b2ab93b71da0f">Protocol_negotiator</a>(<span class="keyword">const</span> <a class="code hl_class" href="classipc_1_1transport_1_1Protocol__negotiator.html">Protocol_negotiator</a>&amp; src);</div>
<div class="line"><a id="l00246" name="l00246"></a><span class="lineno">  246</span><span class="comment"></span> </div>
<div class="line"><a id="l00247" name="l00247"></a><span class="lineno">  247</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00248" name="l00248"></a><span class="lineno">  248</span><span class="comment">   * Move-constructs `*this` to be equal to `src`, while `src` becomes as-if defaulted-cted.</span></div>
<div class="line"><a id="l00249" name="l00249"></a><span class="lineno">  249</span><span class="comment">   *</span></div>
<div class="line"><a id="l00250" name="l00250"></a><span class="lineno">  250</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l00251" name="l00251"></a><span class="lineno">  251</span><span class="comment">   *        Moved-from object that becomes as-if default-cted.</span></div>
<div class="line"><a id="l00252" name="l00252"></a><span class="lineno">  252</span><span class="comment">   */</span></div>
<div class="line"><a id="l00253" name="l00253"></a><span class="lineno">  253</span>  <a class="code hl_function" href="classipc_1_1transport_1_1Protocol__negotiator.html#a427c54f57df581027a330eb0f7146904">Protocol_negotiator</a>(<a class="code hl_class" href="classipc_1_1transport_1_1Protocol__negotiator.html">Protocol_negotiator</a>&amp;&amp; src);</div>
<div class="line"><a id="l00254" name="l00254"></a><span class="lineno">  254</span> </div>
<div class="line"><a id="l00255" name="l00255"></a><span class="lineno">  255</span>  <span class="comment">// Methods.</span></div>
<div class="line"><a id="l00256" name="l00256"></a><span class="lineno">  256</span><span class="comment"></span> </div>
<div class="line"><a id="l00257" name="l00257"></a><span class="lineno">  257</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00258" name="l00258"></a><span class="lineno">  258</span><span class="comment">   * Copy-assigns `*this` to be equal to `src`.</span></div>
<div class="line"><a id="l00259" name="l00259"></a><span class="lineno">  259</span><span class="comment">   *</span></div>
<div class="line"><a id="l00260" name="l00260"></a><span class="lineno">  260</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l00261" name="l00261"></a><span class="lineno">  261</span><span class="comment">   *        Source object.</span></div>
<div class="line"><a id="l00262" name="l00262"></a><span class="lineno">  262</span><span class="comment">   * @return `*this`.</span></div>
<div class="line"><a id="l00263" name="l00263"></a><span class="lineno">  263</span><span class="comment">   */</span></div>
<div class="line"><a id="l00264" name="l00264"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#ae24b3bd8550a2f9ab0d728cb1832d4f5">  264</a></span>  <a class="code hl_class" href="classipc_1_1transport_1_1Protocol__negotiator.html">Protocol_negotiator</a>&amp; <a class="code hl_function" href="classipc_1_1transport_1_1Protocol__negotiator.html#ae24b3bd8550a2f9ab0d728cb1832d4f5">operator=</a>(<span class="keyword">const</span> <a class="code hl_class" href="classipc_1_1transport_1_1Protocol__negotiator.html">Protocol_negotiator</a>&amp; src);</div>
<div class="line"><a id="l00265" name="l00265"></a><span class="lineno">  265</span><span class="comment"></span> </div>
<div class="line"><a id="l00266" name="l00266"></a><span class="lineno">  266</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00267" name="l00267"></a><span class="lineno">  267</span><span class="comment">   * Move-assigns `*this` to be equal to `src`, while `src` becomes as-if just constructed; or no-op</span></div>
<div class="line"><a id="l00268" name="l00268"></a><span class="lineno">  268</span><span class="comment">   * if `&amp;src == this`.</span></div>
<div class="line"><a id="l00269" name="l00269"></a><span class="lineno">  269</span><span class="comment">   *</span></div>
<div class="line"><a id="l00270" name="l00270"></a><span class="lineno">  270</span><span class="comment">   * @param src</span></div>
<div class="line"><a id="l00271" name="l00271"></a><span class="lineno">  271</span><span class="comment">   *        Moved-from object that becomes as-if just-cted, unless it is `*this`.</span></div>
<div class="line"><a id="l00272" name="l00272"></a><span class="lineno">  272</span><span class="comment">   * @return `*this`.</span></div>
<div class="line"><a id="l00273" name="l00273"></a><span class="lineno">  273</span><span class="comment">   */</span></div>
<div class="line"><a id="l00274" name="l00274"></a><span class="lineno">  274</span>  <a class="code hl_class" href="classipc_1_1transport_1_1Protocol__negotiator.html">Protocol_negotiator</a>&amp; <a class="code hl_function" href="classipc_1_1transport_1_1Protocol__negotiator.html#ae24b3bd8550a2f9ab0d728cb1832d4f5">operator=</a>(<a class="code hl_class" href="classipc_1_1transport_1_1Protocol__negotiator.html">Protocol_negotiator</a>&amp;&amp; src);</div>
<div class="line"><a id="l00275" name="l00275"></a><span class="lineno">  275</span><span class="comment"></span> </div>
<div class="line"><a id="l00276" name="l00276"></a><span class="lineno">  276</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00277" name="l00277"></a><span class="lineno">  277</span><span class="comment">   * Returns `S_VER_UNKNOWN` before compute_negotiated_proto_ver(); then either the positive version of the protocol</span></div>
<div class="line"><a id="l00278" name="l00278"></a><span class="lineno">  278</span><span class="comment">   * we shall speak subsequently, or `S_VER_UNSUPPORTED` if the two sides are incompatible.</span></div>
<div class="line"><a id="l00279" name="l00279"></a><span class="lineno">  279</span><span class="comment">   *</span></div>
<div class="line"><a id="l00280" name="l00280"></a><span class="lineno">  280</span><span class="comment">   * @return See above.</span></div>
<div class="line"><a id="l00281" name="l00281"></a><span class="lineno">  281</span><span class="comment">   */</span></div>
<div class="line"><a id="l00282" name="l00282"></a><span class="lineno">  282</span>  <a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> <a class="code hl_function" href="classipc_1_1transport_1_1Protocol__negotiator.html#a9596a28f6379b209ec1e7efcc58b8adc">negotiated_proto_ver</a>() <span class="keyword">const</span>;</div>
<div class="line"><a id="l00283" name="l00283"></a><span class="lineno">  283</span><span class="comment"></span> </div>
<div class="line"><a id="l00284" name="l00284"></a><span class="lineno">  284</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00285" name="l00285"></a><span class="lineno">  285</span><span class="comment">   * Based on the presumably-just-received-from-opposing-side value of their `local_max_proto_ver`, passed-in as</span></div>
<div class="line"><a id="l00286" name="l00286"></a><span class="lineno">  286</span><span class="comment">   * the arg, calculates the protocol version we shall speak over the comm pathway, so it will be returned by</span></div>
<div class="line"><a id="l00287" name="l00287"></a><span class="lineno">  287</span><span class="comment">   * negotiated_proto_ver() subsequently.  Returns `true`; unless it has already been called -- in which case</span></div>
<div class="line"><a id="l00288" name="l00288"></a><span class="lineno">  288</span><span class="comment">   * it is a no-op (outside of logging); returns `false` (unless exception thrown; see next paragraph).</span></div>
<div class="line"><a id="l00289" name="l00289"></a><span class="lineno">  289</span><span class="comment">   *</span></div>
<div class="line"><a id="l00290" name="l00290"></a><span class="lineno">  290</span><span class="comment">   * If it is not a no-op, and the result is that the two sides lack a protocol version they can both speak,</span></div>
<div class="line"><a id="l00291" name="l00291"></a><span class="lineno">  291</span><span class="comment">   * a suggested truthy `Error_code` is emitted using standard Flow error-emission convention.</span></div>
<div class="line"><a id="l00292" name="l00292"></a><span class="lineno">  292</span><span class="comment">   *</span></div>
<div class="line"><a id="l00293" name="l00293"></a><span class="lineno">  293</span><span class="comment">   * Tip: It&#39;s a reasonable tactic to potentially call this for every in-message, if you only do so after ensuring</span></div>
<div class="line"><a id="l00294" name="l00294"></a><span class="lineno">  294</span><span class="comment">   * `negotiated_proto_ver() == S_VER_UNKNOWN`.  That will effectively ensure the negotiation occurs ASAP and at most</span></div>
<div class="line"><a id="l00295" name="l00295"></a><span class="lineno">  295</span><span class="comment">   * once.</span></div>
<div class="line"><a id="l00296" name="l00296"></a><span class="lineno">  296</span><span class="comment">   *</span></div>
<div class="line"><a id="l00297" name="l00297"></a><span class="lineno">  297</span><span class="comment">   * More formally:</span></div>
<div class="line"><a id="l00298" name="l00298"></a><span class="lineno">  298</span><span class="comment">   *   - If `negotiated_proto_ver() != S_VER_UNKNOWN`: does nothing except possibly logging; returns `false`.</span></div>
<div class="line"><a id="l00299" name="l00299"></a><span class="lineno">  299</span><span class="comment">   *     Informal tip: If you don&#39;t know whether that&#39;s the case, check for it via negotiated_proto_ver() and</span></div>
<div class="line"><a id="l00300" name="l00300"></a><span class="lineno">  300</span><span class="comment">   *     neither try to parse `opposing_max_proto_ver` from your in-message, nor call the present method.</span></div>
<div class="line"><a id="l00301" name="l00301"></a><span class="lineno">  301</span><span class="comment">   *   - If `negotiated_proto_ver() == S_VER_UNKNOWN` (the case right after construction): Upon return</span></div>
<div class="line"><a id="l00302" name="l00302"></a><span class="lineno">  302</span><span class="comment">   *     `negotiated_proto_ver() != S_VER_UNKNOWN` and:</span></div>
<div class="line"><a id="l00303" name="l00303"></a><span class="lineno">  303</span><span class="comment">   *     - If `err_code != nullptr`: `*error_code` is set to truthy suggested error to emit if applicable.</span></div>
<div class="line"><a id="l00304" name="l00304"></a><span class="lineno">  304</span><span class="comment">   *       Returns `true`.</span></div>
<div class="line"><a id="l00305" name="l00305"></a><span class="lineno">  305</span><span class="comment">   *     - If `err_code == nullptr`: a truthy suggested error is emitted via exception.</span></div>
<div class="line"><a id="l00306" name="l00306"></a><span class="lineno">  306</span><span class="comment">   *</span></div>
<div class="line"><a id="l00307" name="l00307"></a><span class="lineno">  307</span><span class="comment">   * @param opposing_max_proto_ver</span></div>
<div class="line"><a id="l00308" name="l00308"></a><span class="lineno">  308</span><span class="comment">   *        Value that the opposing Protocol_negotiator (or equivalent) sent to us over pathway:</span></div>
<div class="line"><a id="l00309" name="l00309"></a><span class="lineno">  309</span><span class="comment">   *        their `local_max_proto_ver`.  Any value is allowed (we will check that it&#39;s positive and</span></div>
<div class="line"><a id="l00310" name="l00310"></a><span class="lineno">  310</span><span class="comment">   *        report negotiation failure if not).  Informal advice: if you were unable to parse</span></div>
<div class="line"><a id="l00311" name="l00311"></a><span class="lineno">  311</span><span class="comment">   *        it from your in-message, you should pass S_VER_UNKNOWN.</span></div>
<div class="line"><a id="l00312" name="l00312"></a><span class="lineno">  312</span><span class="comment">   * @param err_code</span></div>
<div class="line"><a id="l00313" name="l00313"></a><span class="lineno">  313</span><span class="comment">   *        See `flow::Error_code` docs for error reporting semantics.  #Error_code generated:</span></div>
<div class="line"><a id="l00314" name="l00314"></a><span class="lineno">  314</span><span class="comment">   *        error::Code::S_PROTOCOL_NEGOTIATION_OPPOSING_VER_TOO_OLD (incompatible protocol version -- we&#39;re more</span></div>
<div class="line"><a id="l00315" name="l00315"></a><span class="lineno">  315</span><span class="comment">   *        advanced and lack backwards-compatibility for their preferred version),</span></div>
<div class="line"><a id="l00316" name="l00316"></a><span class="lineno">  316</span><span class="comment">   *        error::Code::S_PROTOCOL_NEGOTIATION_OPPOSING_VER_INVALID (`opposing_max_proto_ver` is invalid: not</span></div>
<div class="line"><a id="l00317" name="l00317"></a><span class="lineno">  317</span><span class="comment">   *        positive).</span></div>
<div class="line"><a id="l00318" name="l00318"></a><span class="lineno">  318</span><span class="comment">   * @return `false` if pre-condition was `negotiated_proto_ver() != S_VER_UNKNOWN`, so we no-oped;</span></div>
<div class="line"><a id="l00319" name="l00319"></a><span class="lineno">  319</span><span class="comment">   *         `true` otherwise (unless exception thrown, only if `err_code == nullptr`.</span></div>
<div class="line"><a id="l00320" name="l00320"></a><span class="lineno">  320</span><span class="comment">   */</span></div>
<div class="line"><a id="l00321" name="l00321"></a><span class="lineno">  321</span>  <span class="keywordtype">bool</span> <a class="code hl_function" href="classipc_1_1transport_1_1Protocol__negotiator.html#a6e55a4ee1033bf98123cedd10e5726cb">compute_negotiated_proto_ver</a>(<a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> opposing_max_proto_ver, <a class="code hl_typedef" href="namespaceipc.html#aa3192e586cc45d3e7c22463bf2760f89">Error_code</a>* err_code = 0);</div>
<div class="line"><a id="l00322" name="l00322"></a><span class="lineno">  322</span><span class="comment"></span> </div>
<div class="line"><a id="l00323" name="l00323"></a><span class="lineno">  323</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00324" name="l00324"></a><span class="lineno">  324</span><span class="comment">   * To be called at most once, this returns `local_max_proto_ver` from ctor the first time and</span></div>
<div class="line"><a id="l00325" name="l00325"></a><span class="lineno">  325</span><span class="comment">   * #S_VER_UNKNOWN subsequently.</span></div>
<div class="line"><a id="l00326" name="l00326"></a><span class="lineno">  326</span><span class="comment">   *</span></div>
<div class="line"><a id="l00327" name="l00327"></a><span class="lineno">  327</span><span class="comment">   * Tip: It&#39;s a reasonable tactic to call this when about to send any out-message; if it returns</span></div>
<div class="line"><a id="l00328" name="l00328"></a><span class="lineno">  328</span><span class="comment">   * #S_VER_UNKNOWN, then you&#39;ve already sent it and don&#39;t need to do so now; otherwise encode this value</span></div>
<div class="line"><a id="l00329" name="l00329"></a><span class="lineno">  329</span><span class="comment">   * before/with the out-message and send it.</span></div>
<div class="line"><a id="l00330" name="l00330"></a><span class="lineno">  330</span><span class="comment">   *</span></div>
<div class="line"><a id="l00331" name="l00331"></a><span class="lineno">  331</span><span class="comment">   * @return See above.  Either a positive version number or #S_VER_UNKNOWN.</span></div>
<div class="line"><a id="l00332" name="l00332"></a><span class="lineno">  332</span><span class="comment">   */</span></div>
<div class="line"><a id="l00333" name="l00333"></a><span class="lineno">  333</span>  <a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> <a class="code hl_function" href="classipc_1_1transport_1_1Protocol__negotiator.html#a54480f0849ddb5635302b42ed87c43af">local_max_proto_ver_for_sending</a>();</div>
<div class="line"><a id="l00334" name="l00334"></a><span class="lineno">  334</span><span class="comment"></span> </div>
<div class="line"><a id="l00335" name="l00335"></a><span class="lineno">  335</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00336" name="l00336"></a><span class="lineno">  336</span><span class="comment">   * Resets the negotiation state, meaning back to the state as-if just after ctor invoked.  Hence:</span></div>
<div class="line"><a id="l00337" name="l00337"></a><span class="lineno">  337</span><span class="comment">   * negotiated_proto_ver() yields #S_VER_UNKNOWN, while</span></div>
<div class="line"><a id="l00338" name="l00338"></a><span class="lineno">  338</span><span class="comment">   * local_max_proto_ver_for_sending() would yield not-`S_VER_UNKNOWN`.</span></div>
<div class="line"><a id="l00339" name="l00339"></a><span class="lineno">  339</span><span class="comment">   */</span></div>
<div class="line"><a id="l00340" name="l00340"></a><span class="lineno">  340</span>  <span class="keywordtype">void</span> <a class="code hl_function" href="classipc_1_1transport_1_1Protocol__negotiator.html#a2b3448c9655fd1a83b8229957da1c4e2">reset</a>();</div>
<div class="line"><a id="l00341" name="l00341"></a><span class="lineno">  341</span> </div>
<div class="line"><a id="l00342" name="l00342"></a><span class="lineno">  342</span><span class="keyword">private</span>:</div>
<div class="line"><a id="l00343" name="l00343"></a><span class="lineno">  343</span>  <span class="comment">// Data.</span></div>
<div class="line"><a id="l00344" name="l00344"></a><span class="lineno">  344</span><span class="comment"></span> </div>
<div class="line"><a id="l00345" name="l00345"></a><span class="lineno">  345</span><span class="comment">  /// The `nickname` from ctor.  Not `const` so as to support copyability.</span></div>
<div class="line"><a id="l00346" name="l00346"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35ddd3050b39af2881ffc1e97c84f69c">  346</a></span><span class="comment"></span>  std::string <a class="code hl_variable" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35ddd3050b39af2881ffc1e97c84f69c">m_nickname</a>;</div>
<div class="line"><a id="l00347" name="l00347"></a><span class="lineno">  347</span><span class="comment"></span> </div>
<div class="line"><a id="l00348" name="l00348"></a><span class="lineno">  348</span><span class="comment">  /// `local_max_proto_ver` from ctor.  Not `const` so as to support copyability.</span></div>
<div class="line"><a id="l00349" name="l00349"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#a7365678b968b2afb5428ca15a017e120">  349</a></span><span class="comment"></span>  <a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> <a class="code hl_variable" href="classipc_1_1transport_1_1Protocol__negotiator.html#a7365678b968b2afb5428ca15a017e120">m_local_max_proto_ver</a>;</div>
<div class="line"><a id="l00350" name="l00350"></a><span class="lineno">  350</span><span class="comment"></span> </div>
<div class="line"><a id="l00351" name="l00351"></a><span class="lineno">  351</span><span class="comment">  /// `local_min_proto_ver` from ctor.  Not `const` so as to support copyability.</span></div>
<div class="line"><a id="l00352" name="l00352"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#ac78f181ecd2ce58e18c6c90d3c03d230">  352</a></span><span class="comment"></span>  <a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> <a class="code hl_variable" href="classipc_1_1transport_1_1Protocol__negotiator.html#ac78f181ecd2ce58e18c6c90d3c03d230">m_local_min_proto_ver</a>;</div>
<div class="line"><a id="l00353" name="l00353"></a><span class="lineno">  353</span><span class="comment"></span> </div>
<div class="line"><a id="l00354" name="l00354"></a><span class="lineno">  354</span><span class="comment">  /// Init value `false` indicating has local_max_proto_ver_for_sending() has not been called; subsequently `true`.</span></div>
<div class="line"><a id="l00355" name="l00355"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#acd3f04dd8fd5181379d58fa9a25bf447">  355</a></span><span class="comment"></span>  <span class="keywordtype">bool</span> <a class="code hl_variable" href="classipc_1_1transport_1_1Protocol__negotiator.html#acd3f04dd8fd5181379d58fa9a25bf447">m_local_max_proto_ver_sent</a>;</div>
<div class="line"><a id="l00356" name="l00356"></a><span class="lineno">  356</span><span class="comment"></span> </div>
<div class="line"><a id="l00357" name="l00357"></a><span class="lineno">  357</span><span class="comment">  /// See negotiated_proto_ver().</span></div>
<div class="line"><a id="l00358" name="l00358"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1Protocol__negotiator.html#ac30508df0ea2af8a990f9cd60a694fd1">  358</a></span><span class="comment"></span>  <a class="code hl_typedef" href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">proto_ver_t</a> <a class="code hl_variable" href="classipc_1_1transport_1_1Protocol__negotiator.html#ac30508df0ea2af8a990f9cd60a694fd1">m_negotiated_proto_ver</a>;</div>
<div class="line"><a id="l00359" name="l00359"></a><span class="lineno">  359</span>}; <span class="comment">// class Protocol_negotiator</span></div>
<div class="line"><a id="l00360" name="l00360"></a><span class="lineno">  360</span> </div>
<div class="line"><a id="l00361" name="l00361"></a><span class="lineno">  361</span>} <span class="comment">// namespace ipc::transport</span></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html">ipc::transport::Protocol_negotiator</a></div><div class="ttdoc">A simple state machine that, assuming the opposide side of a comm pathway uses an equivalent state ma...</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8hpp_source.html#l00189">protocol_negotiator.hpp:191</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_a126eb85013fbeb11bcee34efbf0c79da"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#a126eb85013fbeb11bcee34efbf0c79da">ipc::transport::Protocol_negotiator::S_VER_UNSUPPORTED</a></div><div class="ttdeci">static constexpr proto_ver_t S_VER_UNSUPPORTED</div><div class="ttdoc">A proto_ver_t value, namely zero, which is a reserved value indicating &quot;unsupported version&quot;; it is n...</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8hpp_source.html#l00208">protocol_negotiator.hpp:208</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_a2b3448c9655fd1a83b8229957da1c4e2"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#a2b3448c9655fd1a83b8229957da1c4e2">ipc::transport::Protocol_negotiator::reset</a></div><div class="ttdeci">void reset()</div><div class="ttdoc">Resets the negotiation state, meaning back to the state as-if just after ctor invoked.</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8cpp_source.html#l00062">protocol_negotiator.cpp:62</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_a35ddd3050b39af2881ffc1e97c84f69c"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#a35ddd3050b39af2881ffc1e97c84f69c">ipc::transport::Protocol_negotiator::m_nickname</a></div><div class="ttdeci">std::string m_nickname</div><div class="ttdoc">The nickname from ctor. Not const so as to support copyability.</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8hpp_source.html#l00346">protocol_negotiator.hpp:346</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_a35fb3885d39f11d0c1f7860e64194592"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#a35fb3885d39f11d0c1f7860e64194592">ipc::transport::Protocol_negotiator::proto_ver_t</a></div><div class="ttdeci">int16_t proto_ver_t</div><div class="ttdoc">Type sufficient to store a protocol version; positive values identify newer versions of a protocol; w...</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8hpp_source.html#l00199">protocol_negotiator.hpp:199</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_a427c54f57df581027a330eb0f7146904"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#a427c54f57df581027a330eb0f7146904">ipc::transport::Protocol_negotiator::Protocol_negotiator</a></div><div class="ttdeci">Protocol_negotiator(flow::log::Logger *logger_ptr, util::String_view nickname, proto_ver_t local_max_proto_ver, proto_ver_t local_min_proto_ver)</div><div class="ttdoc">Constructs a comm pathway's negotiator object in initial state wherein: (1) negotiated_proto_ver() re...</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8cpp_source.html#l00027">protocol_negotiator.cpp:27</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_a54480f0849ddb5635302b42ed87c43af"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#a54480f0849ddb5635302b42ed87c43af">ipc::transport::Protocol_negotiator::local_max_proto_ver_for_sending</a></div><div class="ttdeci">proto_ver_t local_max_proto_ver_for_sending()</div><div class="ttdoc">To be called at most once, this returns local_max_proto_ver from ctor the first time and S_VER_UNKNOW...</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8cpp_source.html#l00131">protocol_negotiator.cpp:131</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_a6e55a4ee1033bf98123cedd10e5726cb"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#a6e55a4ee1033bf98123cedd10e5726cb">ipc::transport::Protocol_negotiator::compute_negotiated_proto_ver</a></div><div class="ttdeci">bool compute_negotiated_proto_ver(proto_ver_t opposing_max_proto_ver, Error_code *err_code=0)</div><div class="ttdoc">Based on the presumably-just-received-from-opposing-side value of their local_max_proto_ver,...</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8cpp_source.html#l00073">protocol_negotiator.cpp:73</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_a7365678b968b2afb5428ca15a017e120"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#a7365678b968b2afb5428ca15a017e120">ipc::transport::Protocol_negotiator::m_local_max_proto_ver</a></div><div class="ttdeci">proto_ver_t m_local_max_proto_ver</div><div class="ttdoc">local_max_proto_ver from ctor. Not const so as to support copyability.</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8hpp_source.html#l00349">protocol_negotiator.hpp:349</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_a9596a28f6379b209ec1e7efcc58b8adc"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#a9596a28f6379b209ec1e7efcc58b8adc">ipc::transport::Protocol_negotiator::negotiated_proto_ver</a></div><div class="ttdeci">proto_ver_t negotiated_proto_ver() const</div><div class="ttdoc">Returns S_VER_UNKNOWN before compute_negotiated_proto_ver(); then either the positive version of the ...</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8cpp_source.html#l00068">protocol_negotiator.cpp:68</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_aa7e47f4f6a700aeaa9600a5426a17292"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#aa7e47f4f6a700aeaa9600a5426a17292">ipc::transport::Protocol_negotiator::S_VER_UNKNOWN</a></div><div class="ttdeci">static constexpr proto_ver_t S_VER_UNKNOWN</div><div class="ttdoc">A proto_ver_t value, namely a negative one, which is a reserved value indicating &quot;unknown version&quot;; i...</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8hpp_source.html#l00215">protocol_negotiator.hpp:215</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_ac30508df0ea2af8a990f9cd60a694fd1"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#ac30508df0ea2af8a990f9cd60a694fd1">ipc::transport::Protocol_negotiator::m_negotiated_proto_ver</a></div><div class="ttdeci">proto_ver_t m_negotiated_proto_ver</div><div class="ttdoc">See negotiated_proto_ver().</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8hpp_source.html#l00358">protocol_negotiator.hpp:358</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_ac78f181ecd2ce58e18c6c90d3c03d230"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#ac78f181ecd2ce58e18c6c90d3c03d230">ipc::transport::Protocol_negotiator::m_local_min_proto_ver</a></div><div class="ttdeci">proto_ver_t m_local_min_proto_ver</div><div class="ttdoc">local_min_proto_ver from ctor. Not const so as to support copyability.</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8hpp_source.html#l00352">protocol_negotiator.hpp:352</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_acd3f04dd8fd5181379d58fa9a25bf447"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#acd3f04dd8fd5181379d58fa9a25bf447">ipc::transport::Protocol_negotiator::m_local_max_proto_ver_sent</a></div><div class="ttdeci">bool m_local_max_proto_ver_sent</div><div class="ttdoc">Init value false indicating has local_max_proto_ver_for_sending() has not been called; subsequently t...</div><div class="ttdef"><b>Definition:</b> <a href="protocol__negotiator_8hpp_source.html#l00355">protocol_negotiator.hpp:355</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_ae24b3bd8550a2f9ab0d728cb1832d4f5"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#ae24b3bd8550a2f9ab0d728cb1832d4f5">ipc::transport::Protocol_negotiator::operator=</a></div><div class="ttdeci">Protocol_negotiator &amp; operator=(const Protocol_negotiator &amp;src)</div><div class="ttdoc">Copy-assigns *this to be equal to src.</div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1Protocol__negotiator_html_ae4a1edcf2f1a0ae3e86b2ab93b71da0f"><div class="ttname"><a href="classipc_1_1transport_1_1Protocol__negotiator.html#ae4a1edcf2f1a0ae3e86b2ab93b71da0f">ipc::transport::Protocol_negotiator::Protocol_negotiator</a></div><div class="ttdeci">Protocol_negotiator(const Protocol_negotiator &amp;src)</div><div class="ttdoc">Copy-constructs *this to be equal to src object.</div></div>
<div class="ttc" id="acommon_8hpp_html"><div class="ttname"><a href="common_8hpp.html">common.hpp</a></div></div>
<div class="ttc" id="anamespaceipc_1_1transport_html"><div class="ttname"><a href="namespaceipc_1_1transport.html">ipc::transport</a></div><div class="ttdoc">Flow-IPC module providing transmission of structured messages and/or low-level blobs (and more) betwe...</div><div class="ttdef"><b>Definition:</b> <a href="asio__local__stream__socket_8cpp_source.html#l00031">asio_local_stream_socket.cpp:32</a></div></div>
<div class="ttc" id="anamespaceipc_1_1util_html_ae6ac47812a90d1287c61e0b7de7bc4f5"><div class="ttname"><a href="namespaceipc_1_1util.html#ae6ac47812a90d1287c61e0b7de7bc4f5">ipc::util::String_view</a></div><div class="ttdeci">flow::util::String_view String_view</div><div class="ttdoc">Short-hand for Flow's String_view.</div><div class="ttdef"><b>Definition:</b> <a href="util__fwd_8hpp_source.html#l00115">util_fwd.hpp:115</a></div></div>
<div class="ttc" id="anamespaceipc_html_aa3192e586cc45d3e7c22463bf2760f89"><div class="ttname"><a href="namespaceipc.html#aa3192e586cc45d3e7c22463bf2760f89">ipc::Error_code</a></div><div class="ttdeci">flow::Error_code Error_code</div><div class="ttdoc">Short-hand for flow::Error_code which is very common.</div><div class="ttdef"><b>Definition:</b> <a href="common_8hpp_source.html#l00298">common.hpp:298</a></div></div>
<div class="ttc" id="autil__fwd_8hpp_html"><div class="ttname"><a href="util__fwd_8hpp.html">util_fwd.hpp</a></div></div>
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